With the development of laser technology with regard to femtosecond-domainultra-shortpulse lasers and the like, in recent years attention has focused on various phenomena that occur with a femtosecond time domain or on a femtosecond time-scale. One such phenomenon is the phenomenon of fluorescence emitted by a substance upon irradiation with a light pulse.
If a substance is irradiated with such a femtosecond ultra-short light pulse, then fluorescence that changes over time with a femtosecond time domain can be obtained, for example the behavior of the fluorescence phenomenon on a femtosecond time-scale can be obtained. Examples of techniques carried out to observe such a fluorescence phenomenon are a method using a streak camera and a method of sampling measurement through pumping and probing.